The present invention relates generally to rotary machines, and more particularly to retrofitting gas turbines.
Gas turbines typically comprise combustion-type gas turbines, which utilize combustion gases to turn rotors, and steam-type gas turbines, which utilize steam to turn rotors. Examples of gas turbines include, but are not limited to, gas-turbine power-generation equipment and gas turbine aircraft engines. A combustion-type gas turbine has a gas path which typically includes, in serial-flow relationship, an air intake (or inlet), a compressor, a combustor, a turbine, and a gas outlet (or exhaust nozzle). A steam-type gas turbine has a gas path which typically includes a steam inlet, a turbine, and a steam outlet.
Compressors and turbines include rotating rotors rotatably attached to surrounding non-rotating stators by suitable bearings. Gas paths between compressors and combustors and between combustors and turbines include annular transition ducts having radially inner and outer stator portions. At certain axial locations, rotors typically include radially-outwardly projecting rotor blades, and at certain axial locations, stators typically include radially-inwardly projecting stator vanes. Some gas turbines include high and low pressure compressors and high and low pressure turbines with the high pressure compressor rotor surrounding the low pressure compressor rotor and with the high pressure turbine rotor surrounding the low pressure turbine rotor. Gas leakage between certain gas-turbine components is undesirable because it wastes gas (e.g., air, combustion gas, steam, etc.) causing a loss in power and efficiency. In some designs, such loss in power and efficiency occurs due to gas leakage past a rotor/stator or rotor/rotor bearing with additional problems including overheating of the bearing causing excessive oil use.
In other applications, conventional gas-turbine power-generation equipment includes gas turbines having a honeycomb-labyrinth seal fixedly secured to the stator and labyrinth hard teeth attached to the rotor. It is known that the labyrinth hard teeth will abrade away a portion of the honeycomb segment due to differential thermal movement during startup or shutdown. While honeycomb-labyrinth seals have proved reliable, their performance degrades over time as a result of transient events in which the stationary and rotating components interfere, rubbing the labyrinth teeth in a xe2x80x9cmushroom profilexe2x80x9d or cutting grooves into the honeycomb material. Either event results in increasing the radial clearance between the stationary and rotating components thereby resulting in increased gas leakage. As a result, replacement of the labyrinth teeth and the honeycomb portion with conventional brush seals is desirable in some designs. However, removal of these components results in an undesirable off-nominal radial clearance between the stationary and rotating components thereby limiting the use of conventional brush seals to replace such honeycomb-labyrinth seals.
Accordingly, there is a need in the art for a method of retrofitting a gas turbine having improved leakage control between stationary and rotating components.
One embodiment of the present invention comprises a method of retrofitting a gas turbine wherein the gas turbine comprises a stator and a rotor. The rotor is coaxially aligned with the stator and spaced apart from the stator so as to define a gap therebetween. The method of retrofitting comprises fixedly securing a sealing member to the stator. The sealing member is configured to restrict a flow of a fluid medium in a fluid path across the gap and generate a pressure drop generally transverse to the gap during operation of the gas turbine.